How Much To Lower Tyre Pressure?

. This is a discussion on How Much To Lower Tyre Pressure? within The Technical Zone. Part of The Automotive Answers category; Hi,
I know that the suspension on all modern cars are designed to take rated load. So a hatch is ...

I know that the suspension on all modern cars are designed to take rated load. So a hatch is designed for 5 people. This means when there are 2 persons or 3 persons, the car crashes through all pot holes. I know a lot of people compensate for this by dropping tyre pressure a bit. My question is how many psi is safe?

Case in point, my Baleno has 195/55 r16. On the swift's 185/65 r14 which recommended 33psi, i kept 31psi all the time & never had issues except for stiff ride. In its last few days with me, i kept 30psi & it was very soft. The Baleno's suspension is well known to be stiff in the rear. It recommends 29psi but i have been keeping 28psi & it was good. Then tried 27psi in rear & it was really good but i am really concerned that the really bad monsoon roads & pot holes will damage the lower profile side walls. What should i do?

Well, it is always safe to follow the OEM guidelines in terms of air pressure since any increase or decrease surely impacts the overall ride quality of the car. I have Honda CITY ivtec on which front psi is 32 and rear psi is 30, but to avoid the car from scrapping from behind on occasions, I increased the rear psi to 32 and mind you, the ride got worse. On breakers the car was literally very bumpy. Same way when my driver used 25 psi in Esteem, with 155 section Tyres, I could feel the car would drag a bit and felt kind of lazy. Hence, no point in playing around with the psi. Let the psi be as it is buddy for better and long life of Tyre(s) and your car.

Well, the Baleno is quite unbearable at 29psi rear. Add to that most pumps in my area are not caliberated properly. The pump where i usually put fuel indicates 28 & 27 in front and back. At another pump last sunday, the same wheels showed up at 26 & 25 respectively. When he put 28 psi the car became really stiff so i went immediately to my regular pump and his indicated 30psi. Even the HPCL pump at Khalapur (when i went last to Pune) showed 2psi lower than what i had put in.

While i dont want to compromise on tyre life, i want a comfortable ride too. Many "maharathis" including the ASC and my trusted mechanic couldn't answer my question on how much to drop pressure. Speaking to my friends in the ASC, they have filed several FTR (field test reports) with Maruti informing them of the issue but MS is not taking any action. All this is getting exasperating

For now i have 28psi in both front and back. Its more of a compromise between comfort and safety. Not sure if its the best thing to do though.

@Ameyam, if the issue lies with the suspension then reducing or increasing the air pressure is a temporary solution. Filing of reports with MSIL may attract attention at some point of time surely and until then I feel, no one can give you an accurate solution to the issue except MSIL itself.

Another potential issue with underinflation is that you risk running the the vehicle on the sidewalls of the tire, which are thinner and relatively fragile. This could wear out the tire earlier and be unsafe if exposed to rough roads, debris or sharp objects.

I have been doing just that +/- 2psi. The door says 29psi, so I started with that and found the car glides on smooth roads and thrashes on the seams / pot holes. So I ran 28psi and it was decent. Not good, just decent. Since two weeks, I am running 27 in the back tyres only. 90% of the time, the back has no one and no luggage. Only once in a while my mom sits in the rear.

@akash1886, the ASC have filed the reports on their own, not from me telling them. Looks like a lot of owners have complained. Its clear that the issue is with the shock absorber. When some one sits in the car, the back suspension sags. This means the spring is quite soft. But when the wheel encounters a pit on bump, it just transfers the load to the chassis. It means the shock is too stiff. Sadly, with 80k+ cars on the road, it doesn't look like MS can afford to replace the shock. I know your uncle has a dealership, why don't you inquire and let us know of any progress?

@Viru, that's exactly my point. If these were 185/65 tyres, I wouldn't bother . But these are lower profiles and I am concerned I will damage them. I have n2 but that was from few months back. Since then, I have been topping up air on weekly basis

One of friend has a baleno and it met with an accident due to tyre burst.Luckily no one got hurt.He used to keep the tyre pressure -1/2 psi less than the recommended to have a comfort ride.Looks like because of that sidewall formed cracked and lead to the tyre burst.So I feel you should never under inflate your tyre specially when you are driving @highway.Keep it as recommended or +2 psi than recomended.You might be having a bit bumpy ride but its safer.

One of friend has a baleno and it met with an accident due to tyre burst.Luckily no one got hurt.He used to keep the tyre pressure -1/2 psi less than the recommended to have a comfort ride.Looks like because of that sidewall formed cracked and lead to the tyre burst.So I feel you should never under inflate your tyre specially when you are driving @highway.Keep it as recommended or +2 psi than recomended.You might be having a bit bumpy ride but its safer.

I am not doing highway runs. The fastest I go on daily office run is 80-90 on the Sahar elevated road.

In any case, I am keeping 28psi for now. I will cross-check it with the hand held pressure gauge I have to be sure there is no issue with the pumps gauge

How usual do you check air,and is the drive done in good roads or mixed ones?
If mixed driving condition,then keep the pressure to 28 PSI itself.

In my swift i usually put air pressure in all tyres as 31-32 PSI, but company says 33 in front and 29 in rear .
I haven't felt bumpiness in this condition.

If i remember correctly, the Swift v trim suggests 33psi back and front.

The Baleno's ride is really clean at 29psi on tar roads till it encounters the customary ditches, patches, seams etc. Thats when you feel the jerk. Concrete roads are by default cast in slabs, so you feel every seam. At higher speeds, in the back it feel like sitting on a road roller if you what i mean. 28 psi reduces nippiness but is more compliant

I dont really have an accurate pressure measuring means. I hav a coido handheld gauge but i depend on the pump's gauge mostly

Of-course, If there is anything he can tell on the same, I'll be more than happy to share here. Will revert on this query by Wednesday.

Quote:

Originally Posted by ameyam

@akash1886, the ASC have filed the reports on their own, not from me telling them. Looks like a lot of owners have complained. Its clear that the issue is with the shock absorber. When some one sits in the car, the back suspension sags. This means the spring is quite soft. But when the wheel encounters a pit on bump, it just transfers the load to the chassis. It means the shock is too stiff. Sadly, with 80k+ cars on the road, it doesn't look like MS can afford to replace the shock. I know your uncle has a dealership, why don't you inquire and let us know of any progress?

Buddy, I have shared the feedback posted by you through whatsapp with my uncle and have met him in person too today and told him about the issue as well. He is in receipt of the same now and he'll reply in about a week's time. He'll study the issue, share & consult on it and give the feedback. Once I have a reply from him, will surely update here. And I can assure you on my part that my uncle will definitely reply on it and this issue won't go unsolved.